Demodex, an inhabitant of human hair follicles,
and a mite which we live with in harmony.

by M. Halit Umar, The Netherlands 

This is the first of a series of articles by the author with the theme
that 'life is a continous interaction between organisms'.

 

The mite Demodex spp., which belongs to Class Arachnida, Order Acarina, lives around hair follicles (Demodex folliculorum hominis) or in the secretory ducts of sebaceous (fat) glands connected to the hair follicles (Demodex brevis) of humans. The preferred sites are facial skin, forehead, cheeks, eyelashes and external ear channels. The size of demodices varies from 0.1 mm to 0.4 mm. Adult parasites have four pairs of short legs. They can slowly move on the skin especially during the night. In humans, the infestation is known as 'demodicosis' and occurs world-wide. The incidence of demodicosis steadily increases with the individual's age. The infestation may be frequently free of symptoms. However, suppurative or glanulomatous reactions and inflammation in acute and chronic forms may occur due to demodicosis in humans.

Demodicosis may also occur in pets and causes conditions known as red mange or canine demodectic mange. The skin irritation of the infected animals is sometimes very extensive and results in loss of hairs and severe skin rashes. The dogs are infected by a species-specific parasite Demodex canis.

If you think your pet possibly suffers from demodicosis you may be able to diagnose it easily, simply by studying freshly collected skin scrapings with a microscope. Use a slightly wetted cotton swab to obtain some material from the suspected parts of the skin. Apply the swab immediately by gentle rubbing onto a glass slide. No cover glass or staining is necessary. If you are lucky, you have many exfoliated cells of the upper part of the skin, degenerated and dead cells with their remnants, and excreted fat as small, slightly greenish spherules (granules). In fact, parasites feed on such material. Mites may be squashed during collection and by smearing material on the glass, but sometimes you may observe slowly moving animals as long as the smear preparation is not dried in air. A slightly closed diaphragm and lowered condenser may improve the microscope image.

Together with the mites we live in harmony! It is unthinkable to imagine an environment where there are no mites! Our face may be their home. They don't usually bother us but they frequently are there. The following images are made from a series of smear preparations obtained from the external ear channel using several cotton swabs directly after having a warm shower. So, it is perfectly reproducible by yourself.

The images shown here are recorded using an Illford B&W negative film in an M35 camera attached to a professional Zeiss microscope through an MC63C semi-automatic phototube.

M. Halit Umar.

Editor's footnote added Nov. 2005. The author has asked for his email contact to be removed. Unfortunately some enquirers are not reading the footnote below before contacting us.

Footnote: The author welcomes discussions and feedback on demodex studies from the hobbyist point of view, but readers with enquiries on the medical or veterinary aspects of this or other human/pet parasites should seek local advice e.g from your doctor or vet as appropriate.

 

The parasites frequently lie in pairs; they are elongated organisms
with an obvious head-neck part and a body-tail part.



They are covered by a cuticle surface.
The body is mostly semi-transparent.



The cuticle covering of body-tail part shows numerous striations.
Head-neck part contains four pairs of short legs.



High magnification of the head-neck part embedded in keratin-containing
desquamated skin cells.



The body-tail part in high magnification.

 

Web sites to visit

There are many interesting web sites to be found on the Internet covering Demodex infestations; both in humans and animals. Only a few links from a long list are given below to encourage further reading.

Demodex folliculorum in chronic blepharitis by A. Jünemann, Department of Ophthalmology, University of Erlangen-Nürnberg, Germany. (Blepharitis is inflammation of the eyelid).

Demodex mites in acne rosacea  Abstract of paper by T Roihu and A L Kariniemi, Department of Dermatology, Helsinki University Central Hospital, Finland. Hosted by the National Library of Medicine web site, USA.

Demodex - introduction, cause, symptoms, diagnosis, treatment, prevention  Long Beach, USA Animal Hospital web site.

For the typical host spectrum of Demodex spp. visit

University of Missouri College of Veterinary Medicine web site.

For colour images of a mature Demodex folliculorum with four pairs of legs click the links:

Human parasitology biology tutorial Kansas State University, USA web site.
(Micscape Editor's note: the technique recommended is for use under controlled conditions. Hobbyists are not advised to try this and do so at their own risk!).

and Laboratoire de Parasitologie Faculté de Pharmacie, Lille France

 

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